非均相类-Fenton体系和活化过硫酸盐体系氧化降解2,4-二氯苯氧乙酸

发布时间：2018-06-12 00:00

本文选题：2 + 4-二氯苯氧乙酸　；参考：《中国地质大学(北京)》2017年博士论文

【摘要】：近年来,有机氯农药2,4-二氯苯氧乙酸(2,4-D)在世界各地地表水与地下水中频频检出,它给人体带来的潜在危害也逐渐引起广泛的关注。因此,处理该类污染水体需要更行之有效的方法。本研究以2,4-D为目标污染物,通过制备合成FeS、FeS/Fe_2O_3和Fe/Fe_2O_3三种固体催化剂非均相催化类-Fenton体系和活化PS体系氧化降解目标污染物。本文考察了不同体系下2,4-D的降解效率及影响因素(初始pH、氧化剂(H_2O_2或PS)浓度、催化剂投加量和反应温度等),分析了2,4-D降解反应动力学特性,推测了自由基氧化降解2,4-D的作用机制并探讨了2,4-D可能的降解路径。主要结论如下:(1)在催化H_2O_2体系和活化PS体系氧化降解2,4-D的研究中,FeS、FeS/Fe_2O_3和Fe/Fe_2O_3均表现出极好的催化性能。不同体系下,溶液初始pH值对2,4-D降解的影响有所不同,但在所有实验体系中,酸性条件均更有利于2,4-D的快速降解。此外,随着催化剂投加量的增加、氧化剂(H_2O_2或PS)浓度的增大和反应温度的升高,2,4-D的去除效率逐渐增加;但过量的氧化剂会对2,4-D降解产生一定的抑制作用。(2)在所有实验体系条件下,2,4-D的降解均符合准一级反应动力学,而且表观反应速率常数符合Arrhenius定律。所有反应体系下较低的表观活化能Ea说明,2,4-D在催化非均相类-Fenton体系和活化PS体系下的氧化降解过程均需能较低,十分容易进行。催化剂回用实验表明,尽管FeS在初次使用后会有钝化现象发生(非均相类-Fenton体系和活化PS体系),但在连续5次的2,4-D降解实验中,依然保持较为理想的催化活性。(3)自由基淬灭实验结果表明,当反应溶液初始pH为4.5时,在非均相类-Fenton体系中,2,4-D的降解主要归于体系中生成的羟基自由基(HO·)对其的氧化作用,尤其是催化剂表面产生的HO·;而在活化PS体系中,体系中的硫酸根自由基(SO4-·)和HO·共同对2,4-D的降解起到氧化作用,而其中HO·可能起到主要作用。(4)结合自由基淬灭实验和电子自旋顺磁共振(EPR)检测结果,推测了非均相类-Fenton体系和活化PS体系下2,4-D可能的氧化机制;利用高效液相色谱仪(HPLC)、离子色谱仪(IC)和气相色谱-质谱仪(GC-MS)对2,4-D降解产物进行了测定,并根据分析结果,提出了2,4-D在非均相类-Fenton体系和活化PS体系下可能的降解路径。
[Abstract]:In recent years, the organochlorine pesticide 2o 4- dichlorophenoxyacetic acid (OCPD) has been frequently detected in surface water and groundwater around the world, and its potential harm to human body has been paid more and more attention. Therefore, more effective methods are needed to deal with this kind of polluted water. In this study, three kinds of solid catalysts, FeS- FeS- / Fe2O3 and Fe- / Fe2O-Ti3, were synthesized and oxidized to the target pollutants by taking 2H4-D as the target pollutant, and the active PS system and the heterogeneous catalyst-Fenton system were used to oxidize and degrade the target pollutants. In this paper, the degradation efficiency and influencing factors (initial pH, oxidizer H _ 2O _ 2 or PS2) concentration, catalyst dosage and reaction temperature of 2H _ 4-D in different systems were investigated, and the kinetic characteristics of the degradation reaction of 2H _ 4-D were analyzed. The mechanism of free radical oxidation and degradation of 2H 4 D was inferred and the possible degradation pathway of 2 O 4 D was discussed. The main conclusions are as follows: (1) in the study of catalytic degradation of 2H _ 4-D in the H _ 2O _ 2 system and the activated PS system, FeSn FeSp / FeS _ 2O _ 3 and Fe / Fe _ S _ 2O _ 3 exhibited excellent catalytic properties. The initial pH value of the solution had different effects on the degradation of 2H _ 4-D in different systems, but in all the experimental systems, the acidic conditions were more favorable to the rapid degradation of 2H _ 4-D. In addition, with the increase of the amount of catalyst, the concentration of H _ 2O _ 2 or PSs increases and the reaction temperature increases, and the removal efficiency of H _ 2O _ 2-D increases gradually. However, excessive oxidizing agent can inhibit the degradation of 2H _ 4-D to a certain extent.) under all experimental conditions, the degradation of ~ (2) ~ (2) ~ (2) ~ (2) D is in accordance with the quasi-first-order reaction kinetics, and the apparent reaction rate constant obeys the Arrhenius's law. The lower apparent activation energy (EA) in all reaction systems indicates that the oxidation and degradation processes of C24-D in heterogeneous -Fenton system and activated PS system need to be low and easy to be carried out. The experimental results of catalyst reuse showed that, although passivation of FeS occurred after initial use (heterogeneous Fenton system and activated PS system), the degradation of FeS was carried out five times in a row. The experimental results of free radical quenching showed that when the initial pH value of the reaction solution was 4.5, the degradation of dithiocarbamate 24-D in heterogeneous -Fenton system was mainly attributed to the oxidation of hydroxyl radical (Ho) produced in the system. Especially the Ho produced on the surface of the catalyst, and in the activated PS system, the sulfate radical (so _ 4-) and Ho can jointly oxidize the degradation of 2o _ 4-D. However, Ho may play a major role in the oxidation mechanism of 2H 4-D under heterogeneous -Fenton system and activated PS system, combined with the results of free radical quenching and electron spin paramagnetic resonance (EPRR). High performance liquid chromatography (HPLC), ion chromatograph (ICC) and gas chromatography-mass spectrometer (GC-MS) were used to determine the degradation products of 2H 4-D. Based on the analysis results, the possible degradation pathways of 2H 4-D in heterogeneous Fenton system and activated PS system were proposed.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X703

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